[CM] standard input EOF in console app s7

[Tito Latini]

> ok thanks, this is not meant as an app, its simply a debugging tool! maybe i should not generate the makefile by default?.

copy, paste and cut for mail-subject is inspired by cm/readme.txt ;)

    s7   
       A console app with ...

A binary called s7 is not a big problem, it is enough to fix the
`yes "s7>"' feature (also the example in s7.html is to fix).


P.S. (to avoid a separate msg for another minor detail)

There is a multi-language example in cm/res/doc/midioutput.scm:62,
probably generated by the translator machine:

(loop with chord = transpose(pick(pick({0 3 7},
                                 {0 4 7},
                                 {0 3 7 10},
                                 {0 4 7 10},
                                 {0 4 7 11}),
                            between(48, 80))
  for k in chord
  mp:midi(key: k)
end